Air cushion table and conveyor unit

ABSTRACT

An air cushion support and sliding device ( 4 ) of a conveyor unit ( 24 ) is equipped with at least one support and sliding table ( 5 ) for objects or products, which is made at least partially of a material which is naturally porous to air and, in particular, is a panel ( 7 ) with a plurality of natural pores ( 8 ) through which the air flows and is distributed in a substantially uniform and capillary fashion on at least one support and sliding surface ( 9 ) on the table ( 5 ).

TECHNICAL FIELD

The present invention relates to an air cushion support and slidingdevice.

The support and sliding device made in accordance with the presentinvention may be used advantageously for conveying objects or productsin various industrial sectors, for example for conveying panels or packsof panels to be cut in a panel saw machine, or in a system using panelsaw machines or for handling loads which may be heavy, to which thefollowing description specifically refers, without limiting the scope ofapplication of the invention.

BACKGROUND ART

Panel saw machines (this being the sector to which reference is made inthis text) are normally used for cutting panels or similar items intosmaller sub-panels. The panels may be made mainly of wood-basedmaterial, but also of other materials such as plastic, light alloys,steel, etc.

Panel saw machines of the known type usually comprise at least onehorizontal support and sliding table on which a mobile piece ofequipment, commonly known-as a pusher, pushes at least one panel to becut (preferably stacks of panels in superposed layers) towards a cuttingdevice (or panel rotation device) located downstream.

During the cutting operation, the panel is held in position on thesliding table by gripper elements, such as clamps, operatively attachedto the rear edge of the panel. Moreover, along the sliding table, thepanel may engage with other, additional positioning, aligning, ejecting,pressing and rotating elements, which are accessories commonly used inpanel saw machines.

Panel cutting is possible only along one cutting axis, or, on morecomplex machines, along two or more cutting axes set at right angles toone another. In the latter case, the panel saw machines are angled andthe relative panel support and sliding tables are at 90 degrees to oneanother. Machines of this type are preferably part of more complex paneltreatment systems which can produce stacks of panels then carry them tomagazines according to the size of the panels.

Panels are normally cut in groups rather than individually. They arestacked vertically one on top of another, forming packs which areusually large and, as a result, relatively heavy. The weight of thepacks of panels therefore necessitates the use of support tablesdesigned to limit the friction on the packs as they slide.

One of the known solutions for facilitating panel pack sliding onsupport tables consists of making the tables in such a way that theyform an air cushion. In this way, the air which flows out of the supportand sliding tables pushes the packs of panels upwards, against gravity,and the resulting normal force acting upon the tables is reduced,consequently reducing friction. In particular, air cushion support andsliding devices of known types comprise at least one support and slidingtable consisting of a plate with holes in it, normally metal, whichforms the upper wall of a ventilated air pipe or distributor box. Thethrough-holes in the plate are usually fitted with stop valves toprevent shavings and machining residues entering the pipe when the airblowing is switched off.

Air cushion support and sliding devices of the above-mentioned knowntype have several disadvantages. A first disadvantage is the fact thatthey generate an air cushion which is uneven and not very capillary evenwith the highest number of holes which can be made in the plate withoutcompromising the capacity for supporting heavy packs of panels. Inparticular, the maximum number of holes is limited by the need toprevent the plate from bending or, more generally, becoming deformed,under the weight of the panels. Plate deformation would lead to twoserious disadvantages, one being deterioration in the table slidingcharacteristics and the other the possibility of air leaks in the zonesin which the plate covers the top of the distributor box. The unevennessand limited spread of the air cushion mean that the air compression mustbe high in order for each hole to generate a thrust sufficient forcorrect support and sliding device operation. As well as requiringexpensive compressors, this creates a high level of noise, being relatedto the high speed at which the air exits the above-mentioned holes.

Moreover, the whole device is quite complex to assemble and relativelyexpensive to produce and maintain. The complexity of assembly alsoprevents the device from being produced with complex shapes andgeometries, normally needed due to ergonomic requirements.

A further disadvantage is the fact that each jet of air exits therespective hole with a pressure, displacement and speed that is highenough to easily carry dust or other polluting agents towards themachining zone. Moreover, both dust and other polluting agents can passthrough the holes freely, as the holes are relatively large.

As an alternative to the above-mentioned air cushion support and slidingdevices there are known devices in which the support and sliding tablesconsist of a plurality of idle rollers, side-by-side in a cascadeformation. These tables also have some disadvantages, specifically ahigh noise level, due to the rotation of the rollers, a relatively highproduction and maintenance cost and limited adaptability to complexergonomic shapes.

DISCLOSURE OF THE INVENTION

The aim of the present invention is to provide an air cushion supportand sliding device which overcomes the above-mentioned disadvantages.

Accordingly, the present invention provides an air cushion support andsliding device comprising at least one support and sliding table forobjects or products. The device is characterised in that the table ismade at least partially of a material which is naturally porous to air.

In particular, the table consists of a panel with a plurality of naturalpores through which the air flows and is distributed in a substantiallyeven and capillary fashion on at least a first support and slidingsurface on the table.

The present invention also relates to a conveyor unit for conveyingobjects or products.

Accordingly, the present invention provides a conveyor unit forconveying objects or products as described in claim 12 or 13 and/or inany of the claims which, directly or indirectly, are dependent on claim13.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the accompanyingdrawings which illustrate a preferred embodiment of it and in which:

FIG. 1 is a schematic view of a panel saw machine equipped with an aircushion support and sliding device made in accordance with the presentinvention;

FIG. 2 is a perspective view of a first embodiment of the air cushionsupport and sliding device made in accordance with the presentinvention;

FIG. 3 is a perspective view of a second embodiment of the air cushionsupport and sliding device made in accordance with the presentinvention; and

FIG. 4 is a perspective view of a conveyor unit for objects or productscomprising the air cushion support and sliding device made in accordancewith the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

With reference to FIG. 1, the numeral 1 denotes a panel saw machine as awhole for cutting objects or products such as panels 2, or sheets orplates, made of wood-based material.

The machine 1, of the known type as regards its structure and operation,is designed to cut the panels 2 transversally into smaller sub-panels 3.

The machine 1 comprises an air cushion support and sliding device 4, inturn comprising a horizontal support and sliding table 5 for the panels2, which are stacked vertically one on top of another forming a pack 6of panels to be cut at a cutting station T.

The table 5 is made in such a way as to allow facilitated panel 2 pack 6sliding on the table 5 in a given linear feed direction F.

As is more clearly illustrated in FIG. 2, the table 5 consists of apanel 7, having the shape of a rectangular parallelepiped, at leastpartially consisting of composite wood-based material, and specificallyat least partially made of MDF (Medium Density Fibreboard). The MDF ispreferably of the water-repellent and/or flame-retardant type.

MDF is a material naturally porous to air and the panel 7 has aplurality of natural pores or micropores 8 designed to allow the air toflow through. The pores 8, enlarged in FIGS. 1 and 2 for graphicrequirements, are naturally distributed in a substantially uniformfashion in the panel 7 and in particular are distributed in asubstantially uniform and capillary manner on a horizontal support andsliding surface 9 of the panel 7. Alternatively, the panel 7 may be atleast partially made of HDF (High Density Fibreboard) or porousaluminium. Like MDF, both HDF and aluminium have a natural and uniformporosity to air.

The outside of the panel 7 is delimited not just by the surface 9, butby five surfaces 10 (one of which is not visible in FIG. 2) which areimpermeable to air. The surfaces 10 are made impermeable by a surfacetreatment, for example painting, on the surfaces 10.

Of these surfaces 10, at least one, labelled 10 a, has a portion whichis not made impermeable and which forms an inlet 11 for blowing air intothe panel 7. The inlet 11 is connected in an airtight fashion to a pipe12, in which a given quantity of air can be blown by a ventilationdevice or a compressor of the known type and not illustrated.

Therefore, as described above, the panel 7 forms a pipe or distributorbox for the air blown in, made in a single part (or single module) usingsimple carpentry and painting operations. This also means that it iseasy to produce the panel 7 not just in the rectangular parallelepipedshape illustrated, but also in more complex and ergonomic shapes andgeometries.

The machine 1 also has means for transferring the panels 2 along thetable 5, comprising a mobile pusher item of equipment 13 designed, whenactivated, to push the panels 2 along the table 5 in the direction Ftowards the cutting station T in which a cutting device 14 is located.

The equipment 13 comprises a crosspiece 15 able to move in the directionof feed F so as to supply the cutting device 14 with periodic feedmovements, with preset quantities, packs 6 of panels 2. During the restperiods between one feed movement and another, the cutting device 14operates in such a way as to cut the packs 6 of panels 2 transversallyto the direction of feed F.

The pusher equipment 13 comprises at least one gripper element 16designed to hold the panels 2 in position during the cutting operation.Each gripper element 16 is operatively connected to a zone of the rearedge of at least one panel 2 and stops this edge from moving whilecutting takes place.

The equipment 13 preferably has a plurality of gripper elements 16 (inFIG. 1 there are 6) alongside one another in a horizontal directionnormal to direction F. Each gripper element 16 comprises a clampconsisting of an upper clamping part 17, for holding down the rear edgeof the panel 2 on the top of the pack 6, and a lower clamping part (notillustrated in FIG. 1) which acts on the rear edge of the lower panel 2in the pack 6: in this case, the two clamping parts act in conjunctionwith one another like two jaws to grip the entire pack 6 at its rearedges. The clamping parts of each gripper element 16 are activated bycontrol means which are known and illustrated.

As is more clearly illustrated in FIG. 2, the lower clamping part ofeach gripper element 16 can slide in the direction F along a groove 18in the panel 7, which is obtained by longitudinal routing on the panel7. The groove may be made impermeable to air, in the same way as thesurfaces 10.

In an embodiment not illustrated, the inlet 11 is substituted with aplurality of smaller inlets. These inlets may be made in one, several orall of the surfaces 10.

In the embodiment illustrated in FIG. 3, the panel 7 which forms thetable 5 is substituted with a panel which is similar but thinner. Inthis case, the panel, still labelled 7, seals the top of an upper outletfrom an air pipe or distribution box 19, which is also part of thedevice 4.

The box 19 has the shape of a box-like parallelepiped and is made, forexample, of metal or plastic.

Similarly to the description referring to FIG. 2, the outside of the box19 is delimited by five surfaces 20 (one of which is not visible in FIG.3) impermeable to air. Of these surfaces 20, at least one, labelled 20a, has an inlet 21 for blowing air into the box 19. The inlet 21 isconnected in an airtight fashion to the above-mentioned pipe 12, intowhich a given quantity of air can be blown by a ventilation device orcompressor of the known type and not illustrated.

Obviously, the surface of the panel 7 facing the inside of the box 19 isnot made impermeable in this case, whilst the sides of the panel 7 mayconveniently be made impermeable.

Moreover, again in an embodiment which is not illustrated, the inlet 21is substituted with a plurality of smaller inlets, which can be made onone, several or all of the surfaces 20.

With reference to both the panel 7 in FIG. 2 and the panel in FIG. 3,the air which flows out of the pores 8 of the surfaces 9 in a capillaryfashion generates an upward thrust which opposes the weight of the packs6 of panels 2. In this way, the resulting force on the support andsliding table 5 is noticeably reduced with a consequent reduction infriction.

The panels 7 in FIGS. 2 and 3 are easy and economical to make and simpleto clean. Moreover, they allow the packs 6 of panels to be supported ina substantially uniform way and are at the same time strong. Inaddition, in contrast to conventional air cushion tables, thanks to thecapillary and uniform porous structure, the panels 7 in FIGS. 2 and 3 donot generate troublesome air jets which hit the body of operatorsworking in contact with the panels 7.

In addition, the air is blown into the panels 7 with low pressurevalues, at approximately atmospheric pressure or lower, and exits eachpore 8 with a low displacement and at a low speed and, therefore, with acontained noise level. Thanks to the reduced size of the pores 8, thepanels 7 also act as a natural filter for dust or other polluting agentswhich may be carried towards the machining zone.

Obviously, the device 4 and machine 1 can be subject to numerousmodifications and variations without thereby departing from the scope ofthe inventive concept. For example, the device 4 may have two or morepanels 7 positioned in various configurations relative to one another,and the machine 1 may have more than one device 4 positioned relative toone another. The panel 7 may also have a different shape to thatillustrated and described above and/or it may not have the grooves 18.

Moreover, it is important to emphasise that the device 4, in all of theembodiments covered by this inventive concept, although particularlyadvantageous when used on panel saw machines, may also be used in othermachines or, simply, in conveyor units for objects or products ingeneral, and with significant advantages in the case of large, heavyobjects or products.

In light of this, in the embodiment illustrated in FIG. 4, the device 4is part of a conveyor unit 24 for objects or products in general,schematically illustrated as a stack of panels labelled PP, which may bevery heavy and have to be transferred along the system line, for examplefrom the panel saw machine outfeed to the magazine for stacking productsobtained in this way.

The device 4 comprises a plurality of panels 7, only three of which areillustrated in FIG. 4 to simplify the description. They are setside-by-side in a cascade formation to form a single support and slidingtable 5 divided into as many sectors (or modules) as there are panels 7.The table 5 is preferably angled downwards in the desired direction D ofobject feed so that, when pushed up by the air exiting the pores 8, theobjects can slide on the table 5 under the action of gravity.

Each panel 7 is identical to that in FIG. 2, except that it does nothave the grooves 18. In particular, each panel 7 is made using the samematerials used to make the panel 7 of FIG. 2 and can be made partiallyimpermeable, in the same way as the panel 7 of FIG. 2.

Air is blown in using the same method as described with reference toFIG. 2, including the alternative embodiments, and in particular theinlet 11 of each panel 7 is connected in an airtight fashion to a pipe12, in which a given quantity of air can be blown by a customaryventilation device or compressor 22.

The controlled movement of the objects in the direction D is guaranteedby a control unit 23 which selectively and successively switches theventilation devices or compressors 22 connected to the pipes 12 on andoff. Obviously, as an object passes between two adjacent panels 7, bothpanels 7 have air blown into them, and the descent of an object may beslowed by simply switching off the device 22 connected to the panel 7 onwhich the object lies.

It is also important to emphasise that switching the devices 22 on andoff allows, on one hand, significant energy saving, since the energyused to compress the air is reduced, and, on the other hand, a furtherreduction in the noise produced by the air exiting the panels 7.

As an alternative to the above-mentioned gravity conveying, the stacksof packs PP may be moved by pusher elements (schematically illustratedand labelled ES in FIG. 4). These may consist of bars which are mobilein the direction D and which can turn in the direction F1 in order toretract outside the stack PP dimensions or to form a pusher element asillustrated with a continuous line in FIG. 4. For synchronised movement,the bars may be controlled by the above-mentioned control unit 23.

Finally, it should also be mentioned that the conveyor unit 24 describedwith reference to FIG. 4 may constitute a conveyor unit for packs ofpanels in a panel saw machine designed to cut panels, in particular in amachine of the type described with reference to FIGS. 1 to 3.

The solution adopted, therefore, allows significant weights to besupported and can easily be applied to any system which has to move aproduct along well-defined trajectories and even long conveyor sections.This is all possible together with easy intervention on the sections ofthe conveyors, to modify their trajectory, reducing the sources of noiseand with the advantage of not having negative effects (scratching) onthe surface of the product which rests on the conveyor table.

1. An air cushion support and sliding device comprising at least onesupport and sliding table (5) for objects or products (2); the devicebeing characterised in that the table (5) is made at least partially ofa material which is naturally porous to air.
 2. The device according toclaim 1, characterised in that the table (5) consists of a panel (7)with a plurality of natural pores (8) through which the air flows and isdistributed in a substantially uniform and capillary fashion on at leasta first support and sliding surface (9) on the table (5).
 3. The deviceaccording to claim 2, characterised in that the table (5) has at least asecond surface (10, 18) which is impermeable to air.
 4. The deviceaccording to claim 3, characterised in that the table (5) has at least athird surface (10 a) forming at least one inlet (11) through which aircan be blown into the table (5).
 5. The device according to claim 1 or2, characterised in that it comprises an air pipe or distributor box(19); the pipe (19) having at least one inlet (21) for blowing air intothe pipe (19) and an upper air outlet sealed by the support and slidingtable (5).
 6. The device according to any of the claims from 1 to 5,characterised in that the support and sliding table (5) is made at leastpartially of a composite wood-based material.
 7. The device according toclaim 6, characterised in that the support and sliding table (5) is madeat least partially of MDF (Medium Density Fibreboard).
 8. The deviceaccording to claim 7, characterised in that the support and slidingtable (5) is made at least partially of water-repellent and/orflame-retardant MDF (Medium Density Fibreboard).
 9. The device accordingto claim 6, characterised in that the support and sliding table (5) ismade at least partially of HDF (High Density Fibreboard).
 10. The deviceaccording to any of the claims from 1 to 5, characterised in that thesupport and sliding table (5) is made at least partially of porousaluminium.
 11. The device according to any of the claims from 1 to 10,characterised in that the support and sliding table (5) forms a naturalfilter for the air which passes through the table (5).
 12. A conveyorunit for conveying objects or products, characterised in that itcomprises at least one air cushion support and sliding device (4) inaccordance with any of the claims from 1 to
 11. 13. A conveyor unit forobjects or products, comprising at least one support and sliding device(4) for the objects or products and characterised in that the supportand sliding device (4) comprises at least one support and sliding panel(7) for the objects or products, the panel (7) at least partiallyconsisting of a material which is naturally porous to air.
 14. Theconveyor unit according to claim 13, characterised in that the supportand sliding device (4) comprises ventilation or compressor means (22)connected to the panel (7) for blowing air into the panel (7).
 15. Theconveyor unit according to claim 13, characterised in that the supportand sliding device (4) comprises a plurality of panels or modules (7),arranged side-by-side in a cascade formation to form a support andsliding table (5), the latter being divided into as many conveyorsectors as there are panels (7), and a plurality of ventilation orcompressor means (22), each connected to a respective panel (7) forblowing air into the panel (7).
 16. The conveyor unit according to claim15, characterised in that the support and sliding device (4) comprises acontrol unit (23) for the ventilation or compressor means (22) designedto selectively switch the ventilation or compressor means (22) on andoff.
 17. The conveyor unit according to claim 16, characterised in thatthe control unit (23) for the ventilation or compressor means (22) isdesigned to switch the ventilation or compressor means (22) on and offin succession.
 18. The conveyor unit according to any of the claims from13 to 17, characterised in that the panel (7) has a plurality of naturalpores (8) through which the air flows and is distributed in asubstantially uniform and capillary fashion on at least a first supportand sliding surface (9) on the panel (7).
 19. The conveyor unitaccording to claim 18, characterised in that the panel (7) is made atleast partially of a composite wood-based material.
 20. The conveyorunit according to claim 19, characterised in that the panel (7) is madeat least partially of MDF (Medium Density Fibreboard).
 21. The conveyorunit according to claim 20, characterised in that the panel (7) is madeat least partially of water-repellent and/or flame-retardant MDF (MediumDensity Fibreboard).
 22. The conveyor unit according to claim 19,characterised in that the panel (7) is made at least partially of HDF(High Density Fibreboard).
 23. The conveyor unit according to claim 18,characterised in that the panel (7) is made at least partially of porousaluminium.
 24. The conveyor unit according to any of the claims from 13to 23, characterised in that the panel (7) forms a natural filter forthe air which passes through the panel (7).
 25. A panel saw machine forcutting panels, characterised in that it comprises at least one aircushion support and sliding device (4) in accordance with any of theclaims from 1 to
 11. 26. A panel saw machine for cutting panels,characterised in that it comprises at least one conveyor unit (24) inaccordance with any of the claims from 12 to 24.